Just a sales gimmick. On some older cars, that have carbon buildup in the induction system caused by abnormal operating conditions, it could make sense, but to do it “occasionally”, no, unless it says to in the owner’s manual, which is highly unlikely. I would love to see

you pin this person down in a constructive but relentless way and make him explain exactly why this has to be done if it’s not mentioned in the owner’s manual. If he says it’s because you may get deposits inside the intake manifold or something like that, ask him why that should happen on a quality make like Toyota that’s well maintained. Please post back.

Of course, I understand you not wanting to get in a stressful situation vis-a-vis you and the dealer, but it boils my blood when I hear about these sales gimmicks. Once in a while, they may be legit, but hardly ever.

Some salesman from the maker of the induction cleaning machine stopped by the shop a few weeks ago and told the service writer the wonders their machine will do to their customers car, and how much money they can make off it. The service writer then tells the salesman “You had me at ‘Hello’”, proceeds to tell everyone they need it done in order to garner more profit for the dealership, and makes people feel that their vehicle will keel over if they don’t do the induction cleaning.

Newer cars have the fuel injectors in the intake port near the intake valve, so all that is pulled through the induction plumbing is filtered air. The plumbing upstream of the air cleaner might get dusty, but that’s usually nothing to worry about.

Actually, there can be considerable back flow from the exhaust system to the intake manifold. On most engines, the intake valve already starts opening before the exhaust valve is completely closed. During that overlap period, the intake manifold’s vacuum can suck exhaust gas backward into the intake manifold, especially while idling.

With race car cams, this effect can be so extreme that the engine idles like a two-stoke engine.

This is why carbon and other combustion chamber deposits find their way into the intake ports. Are these deposits harmful? Probably not.

There’s also stuff from the PCV system, which can be pretty grungy in some cases.
The PCV valve gets vacuum from a port downstream of the throttle
Many systems also have a vent from the crankcase to upstream of the throttle. That one can cause deposits on the throttle and idle air valve.

The Atlas I6 in the Trailblazer is notorious for this issue. I changed plugs at about 60k miles and then you’re only 4 bolts and one electrical connector from removing the TB at that point. The amount of accumulated grunge was substantial and affecting performance. After cleaning, the computer took some time to figure it out again and there is a noticeable improvement in idle smoothness and throttle lag reduction.

I went ahead and had it done because… the knock sensor was out for a long time, then the ACV supply tube was filled with carbon (?) deposits that caused a PO400 code, so I went ahead and did it, but hate throwing money away. If that ACV tube got plugged up, I could make a case for other gunk possibly plugging up the system also (99 maxima with 140k miles)

In many cases, it is just a money making gimmick, but in some cases it can help engine performance and even do almost everything the salesman says it will do. This is only in some cases. If you are interested in having this done, I would ask around at some independent shops about having it done. Many dealerships and franchise shops have “three stage” systems from companies like BG, but in many instances, they are just too expensive to warrant using them when you can get the same effect from a $4 can of carb cleaner and a half hour labor. I will say the BG chemicals are some of the best around, and their fuel rail cleaner will bring a dead injector back to life in a mid '90s GM V6. If they are charging $40-50 for this service, it may be worth it. If they are charging $100+ and you don’t have a driveability problem, it’s not worth it.